The fossil record, although expansive and bursting-from-the-seams with material, is fragmentary. This is observed time and time again with discoveries so fragmentary proper names are impossible to be attributed. The tomb that is Mongolia is a great reservoir of fossils, many quite well preserved. Along with well-preserved specimens come the fragmentary ones. Alectrosaurus is one of those fragmentary finds that struggles to shed light on the ecosystems of the prehistoric world, and of course Mongolia as well.

​ Third Asiatic Expedition of the American Museum of Natural History found only the right hind limb on April 25th, 1925. This find was neither the first, nor the last, and a week later assistant paleontologist, George Olsen, (Who discovered the first specimen and namesake of the species name; A. olseni) found more material on the fourth of May. Nearly one hundred feet away from the initial specimen, he discovered a right humerus, two incomplete manual digits, and four fragmentary caudal vertebrae. These finds were sent back to the museum and prepared; however, more material was uncovered some time later. Fossils were then found in Outer Mongolia which included skull and shoulder fragments. Enough material to suggest how the animal may have appeared in life (Thanks to the laws of symmetry), still more material is needed to get a more solid picture of this animal.

​The material that was found suggests a Tyrannosauroid theropod of medium size and moderate build. Alectrosaurus may have reached lengths of up to twenty feet. Unlike other Tyrannosauroids, the superfamily leading to more advanced groups like Tyrannosauridae, the lengths of the tibia and femur are rather similar. The formation, in which Alectrosaurus was found, called the Iren Dabasu Formation, suggests it may have lived in an area that also housed animals like Gigantoraptor, Bactrosaurus, and Gilmoreosaurus.